Marcus Aurelius Numerius Carus was born around AD 224 in Narbo in Gaul.

He must have had an extensive and successful military career as in AD 276 emperor Probus made him praetorian prefect. But in AD 282 when he was inspecting troops in Raetia and Noricum in preparation for Probus' campaign against the Persians, the discontent of the soldiers with their emperor boiled over and they hailed Carus the new ruler. Carus though is alleged to have rejected this offer at first out of loyalty to his emperor.
If this is true or not, when Probus heard of the revolt he immediately sent forces to crush it. But the soldiers simply deserted and joined with those of Carus. Morale in Probus' camp finally collapsed and the emperor was murdered by his own troops.

When Carus learnt of Probus' death, he sent a messenger to inform the senate, that Probus was dead and that he had succeeded him. It says much about Carus that he didn't seek the senate's approval, as had always been the tradition. Far more he told the senators that he, Carus, was now emperor.
However, had Probus enjoyed respect among the senate, Carus though did think it wise to see to his predecessor's deification.

Then Carus saw to establishing his dynasty. He possessed two adult sons, Carinus and Numerian. Both were elevated the rank of Caesar (junior emperor). But these elevations appear to have been arranged without Carus even visiting Rome.

News soon reached him that the Sarmatians and the Quadi had crossed the Danube and invaded Pannonia. Carus, together with his son Numerian, moved into Pannonia and there decisively defeated the barbarians, some reports telling of as many as sixteen thousand barbarian casualties, and twenty thousand prisoners taken.

In the winter of AD 282/3 Carus then set out for Persia, accompanied once again by his son Numerian, announcing that he sought to achieve the re-conquest of Mesopotamia planned by Probus.
The time seemed right, as the Persian king Bahram II was engaged in a civil war against his brother Homizd.
Also Persia had been in decline ever since the death of Sapor I (Shapur I). It was no longer represented a great threat to the Roman empire.

In AD 283 Carus invaded Mesopotamia unopposed, later defeated a Persian army and captured first Seleucia and then the Persian capital Ctesiphon itself. Mesopotamia was successfully reoccupied.
In celebration of this event the emperor's elder son Carinus, who'd been left in charge of governing the west of the empire in Carus' absence, was declared Augustus.

Next Carus planned to follow up his success against the Persians and drive yet further into their territory. But then Carus suddenly died. It was around the end of July and the emperor's camp was close to Ctesiphon. Carus was simply found dead in his tent. There had been a thunderstorm and his death was explained by suggesting his tent had been struck by lightning. A punishment by the gods for seeking to push the empire beyond its rightful boundaries.
But this appears to be too convenient an answer. Other accounts tell of Carus dying of illness. With rumours pointing to Arrius Aper, the praetorian prefect and father-in-law of Numerian, who appeared to fancy the job of emperor for himself, Carus might have been poisoned.
A further rumour hints at Diocletian, then the commander of the imperial bodyguard, being involved in the killing.